Builders need to know what works and what doesn't when it comes to mounting flat panels. So TecHome Builder asked Derrik Lam, director of mounting solutions business unit for Peerless Industries, some basic mounting questions.
THB: What are the weight limits or recommendations for single- and double-stud mounted displays?
Lam: The answer is not so simple. This is because weight limit depends on the combination of the screen, mount, number of studs and stud construction. Limits range on a single stud from 25-150 lbs. or more, while a double-stud installation may hold up to 300 lbs. or more. Look for a mount manufacturer with a solid reputation for safe products that are UL listed. UL listing means that the product must, among other things, be able to withstand four times its rated load.
THB: How is load capacity determined?
Lam: Each product must be tested on all recommended surfaces (wood, metal, concrete, etc.) to ensure a safe installation, so there really is no rule of thumb for determining the load capacity. In the engineering realm, the terms "center of gravity" and "moment arm" are often used as methods for calculating load capacity. In other words, the farther a load is away from the wall, the more the mounting surface must bear.
THB: What's the best surface to mount a flat panel on?
Lam: Wood stud mounting can be the easiest and most reliable surface on which to mount the flat panel. An 84-inch 335-lb. flat-panel TV could safely be mounted on wood studs -- if the precautionary measures are taken. Make sure that the wood studs are in good condition (i.e. no rotting or damage) and that they are part of a good frame on top and bottom of the wall. Most importantly, carefully read and follow the instructions, or refer to an experienced installer.
THB: Should a metal stud installation be "strengthened" using a wood wall plate mounted behind the TV?
Lam: Whenever redundant safety measures can be employed, they should. However, metal stud mounting can be very strong when used with the right togglers if the mount manufacturer recommends the product to be used in this manner. Some products cannot be mounted to metal studs due to the weaker mounting surface, so never replace wood screws with metal stud togglers without the expressed written directions from the mount manufacturer.
Note that due to the vast variations in metal stud and drywall choice used in general construction, UL does not recognize nor approve the use of metal stud mounting. Additionally, a metal stud's weakness lies not only in its thin construction but also in its shape. The "c" channel design does not resist side-to-side twist, so the use of internal wood studs or wood backer plate when possible is recommended to prevent accidental twisting of the studs.
THB: What are the general recommendations for mounting a TV above a fireplace?
Lam: Always refer to the manufacturer's recommended operating temperature before installing a flat panel above a fireplace. While many mounts include instructions for wood stud, concrete or concrete/cement block installation, they may not have recommendations for other surfaces. Many fireplaces, for example, have decorative facades of stone, wood, marble, etc. that may not be structurally anchored into the wall, so knowledge of the construction material is critical.
Most issues are due to a faulty installation or mounting surface, not a faulty mount. Therefore, if the mount manufacturer does not have recommendations on a certain surface, don't assume. Some manufacturers have custom-capabilities departments that will investigate odd surfaces to ensure a safe installation, so unless the installer has prior experience mounting to the exact surface with the exact mount, substituting anchors or products is not recommended.